Scroll fluid machine

ABSTRACT

A scroll fluid machine includes a pair of a fixed scroll ( 15 ) and an orbiting scroll ( 16 ). The scroll fluid machine has an one-side stepped scroll structure in which a stepped part ( 16 E) is provided only at a predetermined position on a tooth bottom surface ( 16 D) of a involute spiral wrap ( 16 B) of one of the fixed scroll ( 15 ) and the orbiting scroll ( 16 ) in a spiral direction, and a stepped part ( 15 E) corresponding to the stepped part ( 16 E) on the tooth bottom surface ( 16 D) is provided only at a predetermined position on a tooth top surface ( 15 C) of a involute spiral wrap ( 15 B) of the other scroll in a spiral direction. The stepped part ( 16 E) on the tooth bottom surface ( 16 D) is provided at a position on an inner side of a spiral end position ( 16 F) of the involute spiral wrap ( 16 B) at intake closure by an involute angle of n radians in the spiral direction or at a position on an outer side of the inner-side position.

TECHNICAL FIELD

The present invention relates to a scroll fluid machine applicable to, for example, a compressor, a pump, and an expander.

BACKGROUND ART

A scroll fluid machine includes a pair of a fixed scroll and an orbiting scroll including involute spiral wraps erected on end plates and meshed with each other in a facing manner at phases shifted by 180°. With this configuration, the scroll fluid machine forms, between both scrolls, a pair of compression pockets for supplying and discharging fluid. Such a scroll fluid machine such as a scroll compressor typically has a two-dimensional compression structure in which the involute spiral wraps of the fixed scroll and the orbiting scroll have identical wrap heights on entire circumference in the spiral direction. In such a two-dimensional compression structure, the compression pockets are moved from an outer side to an inner side while the volumes thereof decrease, thereby compressing fluid taken in the compression pockets in the circumferential direction of the involute spiral wraps.

A stepped scroll compressor has a three-dimensional compression structure to achieve increased efficiency by increasing a compression volume ratio and reduction in size and weight. In this structure, stepped parts are provided at predetermined positions on a tooth top surface and a tooth bottom surface of a involute spiral wrap of each of fixed and orbiting scrolls in the spiral direction. Each involute spiral wrap has a higher wrap height on the outer side of each stepped part than on the inner side, and each compression pocket has a higher height in the direction of the axis line on the outer side of each stepped part than on the inner side. With this configuration, fluid is compressed in the circumferential and height directions of the involute spiral wrap.

Examples of such stepped scroll compressors include those disclosed in PTL 1, 2, 3, and 4. PTL 1 and 2 each disclose a scroll compressor having a both-side stepped structure in which stepped parts are provided at predetermined positions on the tooth top and tooth bottom surfaces of the involute spiral wrap of each of fixed and orbiting scrolls in the spiral direction. PTL 3 and 4 each disclose a scroll compressor having a one-side stepped structure in which a stepped part is provided only at a predetermined position on the tooth bottom surface of the involute spiral wrap of one of fixed and orbiting scrolls in the spiral direction, and the other scroll includes a stepped part only at a predetermined position on the tooth top surface of the corresponding involute spiral wrap in the spiral direction.

CITATION LIST Patent Literature {PTL 1}

Japanese Unexamined Patent Application, Publication No. 2002-5053

{PTL 2}

Japanese Unexamined Patent Application, Publication No. 2009-74461

{PTL 3}

Japanese Examined Patent Application, Publication No. Sho 60-17956 (refer to FIG. 8)

{PTL 4}

Japanese Unexamined Patent Application, Publication No. Hei 4-121483

SUMMARY OF INVENTION Technical Problem

In a scroll compressor having the three-dimensional compression structure in which stepped parts are provided to the fixed and orbiting scrolls as disclosed in PTL 1 and 2, a pair of compression pockets are symmetric and have balanced internal pressures. Thus, when mesh between the stepped parts is canceled so that the compression pockets are communicated with each other to mix gas, no mixing loss occurs. However, this structure requires extra fabrication work for providing stepped parts to both scrolls. In addition, since stepped-part mesh gaps, which can lead to gas leakage, are provided at two places, a larger amount of gas is likely to leak. These are examples of problems of the three-dimensional compression structure.

In the one-side stepped structure as disclosed in PTL 3 and 4, mesh between stepped parts occurs at one place, which leads to reduction of gas leakage and halves fabrication work. However, a pair of compression pockets are asymmetric due to the presence and absence of stepped parts, and have unbalanced volumes. With this configuration, a pressure difference occurs between the pair of compression pockets when the compression pockets are subjected to intake closure to start compression and then the mesh between the stepped parts is canceled so that the compression pockets are communicated with each other. This pressure difference leads to a mixing loss, causing decrease in efficiency accordingly, for example.

The present invention is intended to solve the above-described problem by providing a scroll fluid machine that achieves increased efficiency by increasing a compression volume ratio through a stepped structure, reduction in size and weight, and further increased efficiency by preventing occurrence of a mixing loss.

Solution to Problem

To solve the above-described problem, a scroll fluid machine according to the present invention employs the following solutions.

A scroll fluid machine according to the present invention includes a pair of a fixed scroll and an orbiting scroll that include respective involute spiral wraps erected on end plates and meshed with each other in a facing manner. This scroll fluid machine has a one-side stepped scroll structure in which a stepped part is provided only at a predetermined position on a tooth bottom surface of the involute spiral wrap of one of the fixed scroll and the orbiting scroll in a spiral direction, and a stepped part corresponding to the stepped part on the tooth bottom surface is provided only at a predetermined position on a tooth top surface of the involute spiral wrap of the other scroll in a spiral direction. The stepped part on each tooth bottom surface is provided at a position on an inner side of a spiral end position of the corresponding involute spiral wrap at intake closure by an involute angle of π radians in a spiral direction or at a position on an outer side of the inner-side position.

In the scroll fluid machine having the one-side stepped structure in which stepped parts are provided in only one of a pair of compression pockets, internal pressures inside the compression pockets are unbalanced. Accordingly, a mixing loss occurs when the mesh between the stepped parts is canceled so that the internal pressures are mixed.

According to the present invention, the stepped part on the tooth bottom surface is provided at a position on the inner side of the spiral end position of the corresponding involute spiral wrap at intake closure by an involute angle of n radians in the spiral direction or at a position on an outer side of the inner-side position. With this configuration, the mesh between the stepped parts can be canceled so that the compression pockets are communicated with each other when the internal pressures in the pair of compression pockets are still effectively identical to each other before changing.

Thus, a mixing loss can be prevented from occurring due to the stepped parts provided in only one of the pair of compression pockets, thereby achieving improved efficiency accordingly.

Moreover, the efficiency can be further improved by reducing the number of places of stepped-part mesh gaps in the scroll fluid machine having the one-side stepped structure from two to one to halve leakage of a working medium. In addition, cost reduction can be achieved by halving work for fabricating the stepped parts.

Another scroll fluid machine according to the present invention includes a pair of a fixed scroll and an orbiting scroll that include respective involute spiral wraps erected on end plates and meshed with each other in a facing manner. This scroll fluid machine has a both-side stepped scroll structure in which stepped parts are provided at predetermined positions on a tooth top surface and a tooth bottom surface of the involute spiral wrap of each of the fixed scroll and the orbiting scroll in a spiral direction. The stepped parts have heights different between the fixed scroll and the orbiting scroll. The stepped part on each tooth bottom surface is provided at a position on an inner side of a spiral end position of the corresponding involute spiral wrap at intake closure by an involute angle of π radians in a spiral direction or at a position on an outer side of the inner-side position.

In the scroll fluid machine having the both-side stepped structure in which stepped parts are provided in each of the pair of compression pockets and have heights different between the pair of compression pockets, the internal pressures inside the compression pockets are unbalanced. Accordingly, a mixing loss occurs when the mesh between the stepped parts is canceled so that the internal pressures are mixed.

According to the present invention, the stepped part on each tooth bottom surface is provided at a position on the inner side of the spiral end position of the corresponding involute spiral wrap at intake closure by an involute angle of n radians in the spiral direction or at a position on an outer side of the inner-side position. With this configuration, the mesh between the stepped parts can be canceled so that the compression pockets are communicated with each other when the internal pressures in the pair of compression pockets are still effectively identical to each other before changing.

Thus, a mixing loss can be prevented from occurring due to different heights of stepped parts in the scroll fluid machine having the both-side stepped structure in which the stepped parts have different heights between the pair of compression pockets, thereby achieving improved efficiency accordingly.

In any one of the above-described scroll fluid machines according to the present invention, the stepped part on the tooth bottom surface is provided in a positional range on the inner side of the spiral end position of the corresponding involute spiral wrap by an involute angle of π/2 radians to π radians in the spiral direction.

The present invention can achieve an effect provided by an increased compression volume ratio due to the stepped parts thus provided, and simultaneously prevent a mixing loss occurring when the mesh between the stepped parts is canceled so that the internal pressures in the pair of compression pockets are mixed.

Thus, the scroll fluid machines can each achieve increased efficiency through a stepped structure, reduction in size and weight, and further increased efficiency by preventing a mixing loss.

Advantageous Effects of Invention

According to the present invention, in a scroll fluid machine having a one-side stepped structure in which stepped parts are provided in only one of a pair of compression pockets, mesh between the stepped parts can be canceled so that the compression pockets are communicated with each other when internal pressures in the pair of compression pockets are effectively identical to each other before changing.

Thus, a mixing loss can be prevented from occurring due to the stepped parts provided in only one of the pair of compression pockets, thereby achieving improved efficiency accordingly.

The efficiency can be further improved by reducing the number of places of stepped-part mesh gaps in the scroll fluid machine having the one-side stepped structure from two to one to halve leakage of a working medium. In addition, cost reduction can be achieved by halving work for fabricating the stepped parts.

According to the present invention, in a scroll fluid machine having a both-side stepped structure in which stepped parts are provided in each of a pair of compression pockets and have heights different between the pair of compression pockets, mesh between the stepped parts can be canceled so that both compression pockets are communicated with each other when the pair of compression pockets have internal pressures effectively identical to each other before changing.

Thus, in the scroll fluid machine having the both-side stepped structure in which stepped parts in a pair of compression pockets have heights different between the pair of compression pockets, a mixing loss can be prevented from occurring due to the different heights of the stepped parts, thereby achieving improved efficiency accordingly.

BRIEF DESCRIPTION OF DRAWINGS {FIG. 1}

FIG. 1 is a longitudinal sectional view of a scroll fluid machine according to a first embodiment of the present invention.

{FIG. 2}

FIG. 2 includes explanatory diagrams (A) to (D) of the state of mesh between a fixed scroll and an orbiting scroll of the scroll fluid machine at different scroll position angle positions.

{FIG. 3}

FIG. 3 includes explanatory diagrams (A) to (D) of the mesh state according to Comparative Example, corresponding to FIG. 2.

{FIG. 4}

FIG. 4 is a graph illustrating change of cylinder internal pressure with an scroll position angle in the scroll fluid machine according to the first embodiment.

{FIG. 5}

FIG. 5 is a graph illustrating change of the cylinder internal pressure with the scroll position angle in Comparative Example.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First Embodiment

The following describes a first embodiment of the present invention with reference to FIGS. 1 to 5.

FIG. 1 illustrates a longitudinal sectional view of a scroll fluid machine according to the first embodiment of the present invention. FIGS. 2(A) to 2(D) in FIG. 2 illustrate explanatory diagrams of the state of mesh between a fixed scroll and an orbiting scroll of the scroll fluid machine at different scroll position angle positions.

This example describes, as an exemplary scroll fluid machine, an open scroll compressor (scroll fluid machine) 1 configured to be driven by externally supplied power.

As illustrated in FIG. 1, the open scroll compressor (scroll fluid machine) 1 includes a housing 2 serving as a shell. The housing 2 has a cylindrical shape with an opened front end and a sealed rear end. A front housing 3 is fastened to the opening at the front end of the housing 2 by a bolt 4 to form a sealed space inside the housing 2. A scroll compression mechanism 5 and a drive shaft 6 are incorporated in the sealed space.

The drive shaft 6 is rotatably supported by the front housing 3 through a main bearing 7 and an auxiliary bearing 8. A pulley 11 rotatably installed on an outer periphery of the front housing 3 through bearing 10 is coupled, through an electromagnetic clutch 12, with a front end part externally protruding from the front housing 3 through a lip seal (or a mechanical seal) 9, thereby receiving power transferred from the outside. A rear end of the drive shaft 6 is integrated with a crank pin 13 decentered by a predetermined dimension and coupled with an orbiting scroll 16 of the scroll compression mechanism 5 to be described later through a well-known driven crank mechanism 14 having a variable orbital radius and including a drive bush and a drive bearing.

The scroll compression mechanism 5 forms a pair of compression pockets (compression pockets) 17 between a pair of a fixed scroll 15 and the orbiting scroll 16 being meshed with each other at phases shifted from each other by 180°. Fluid (refrigerant gas) is compressed when the compression pockets 17 are moved from peripheral positions to central positions while their volumes are reduced. The fixed scroll 15 includes a discharge port 18 through which the gas compressed at a central site of the fixed scroll 15 is discharged and that is fixed to a bottom wall surface of the housing 2 through a bolt 19. The orbiting scroll 16 is coupled with the crank pin 13 of the drive shaft 6 through the driven crank mechanism 14, and supported on a thrust bearing surface of the front housing 3 through a well-known spin preventing mechanism 20 so as to be freely driven in orbital rotation.

An O ring 21 is provided on an outer periphery of an end plate 15A of the fixed scroll 15. The O ring 21 is in close contact with an inner peripheral surface of the housing 2 to partition the internal space of the housing 2 into a discharge chamber 22 and an intake chamber 23. The discharge port 18 is opened in the discharge chamber 22 to discharge high-pressure compressed gas from the compression pockets 17 into a refrigeration cycle. An intake port 24 provided to the housing 2 is opened in the intake chamber 23 so that low-pressure gas circulated through the refrigeration cycle is taken into the compression pockets 17 through the intake chamber 23.

The pair of the fixed scroll 15 and the orbiting scroll 16 respectively include involute spiral wraps 15B and 16B erected on the end plate 15A and an end plate 16A. In the present embodiment, as illustrated in FIG. 2, one of the fixed scroll 15 and the orbiting scroll 16, which is the orbiting scroll 16 in this example, includes a stepped part 16E only at a predetermined position on a tooth bottom surface 16D of the involute spiral wrap 16B in a spiral direction. The other fixed scroll 15 includes a stepped part 15E only at a predetermined position (corresponding to the stepped part 16E provided on the tooth bottom surface 16D of the involute spiral wrap 16B of the orbiting scroll 16) on a tooth top surface 15C of the involute spiral wrap 15B in a spiral direction.

As described above, the stepped part 16E is provided only on the tooth bottom surface 16D of the orbiting scroll 16, and the stepped part 15E corresponding to the stepped part 16E is provided only on the tooth top surface 15C of the involute spiral wrap 15B of the fixed scroll 15. The tooth bottom surface 15D of the fixed scroll 15, which is provided with no stepped part, is entirely flat. In addition, a tooth top surface 16C of the involute spiral wrap 16B of the orbiting scroll 16 uniformly has an identical height. Accordingly, the scroll compressor 1 has a one-side stepped structure in which stepped parts is provided in only one of the compression pockets 17.

In the scroll compressor 1 having the one-side stepped structure, one of the pair of compression pockets 17 at intake closure includes a stepped part and the other compression pocket 17 includes no stepped part. Accordingly, the compression pockets are asymmetric to each other and have unbalanced volumes. Thus, the pair of compression pockets 17 have different compression volume ratios. When a pressure difference is generated between the compression pockets 17 in a compression process, the mesh between the stepped parts is canceled so that the pair of compression pockets 17 are communicated with each other, thereby causing a compression loss due to mixture.

For example, as illustrated in FIG. 3, in an intake closure state in FIG. 3(A), the stepped part 16E of the tooth bottom surface 16D is provided at a position on an inner side of a spiral end position 16F of the involute spiral wrap 16B of the orbiting scroll 16 by an involute angle of 1.5π radians in the spiral direction. At the position illustrated in FIG. 3(A), the stepped parts 16E and 15E are meshed with each other, achieving a sealed state between the pair of compression pockets 17. Compression starts from this state. When the scroll position angle proceeds by 90° to the position illustrated in FIG. 3(B), the stepped parts 16E and 15E are still meshed with each other. When the scroll position angle proceeds by 90° from the position illustrated in FIG. 3(B) to the position illustrated in FIG. 3(C), however, the mesh between the stepped parts 16E and 15E is canceled so that the pair of compression pockets 17 being compressed to have a pressure difference therebetween is communicated with each other, thereby causing a mixing loss.

This state is indicated in a graph in FIG. 5 illustrating change in cylinder internal pressure (internal pressure of each compression pocket). The mixing loss leads to efficiency decrease. When the scroll position angle proceeds by 90° from the position illustrated in FIG. 3(C) to the position illustrated in FIG. 3(D), the stepped parts 16E and 15E are meshed with each other again. When the scroll position angle proceeds by another 90°, 360° rotation is completed to achieve a return to the position illustrated in FIG. 3(A). Accordingly, the pair of compression pockets 17 at intake closure at the position illustrated in FIG. 3(A) move to compression pocket positions one step inside. Further rotation joins the pair of compression pockets 17 to discharge compressed gas into the discharge chamber 22 through the discharge port 18. In FIG. 5, rotation proceeds as the scroll position angle decreases.

The present embodiment is intended to prevent, by specifying the positions of the stepped parts 16E and 15E, the mixing loss occurring when the mesh between the stepped parts 16E and 15E is canceled so that the pair of compression pockets 17 are communicated with each other. To achieve this, as illustrated in FIG. 2, the stepped part 16E of the tooth bottom surface 16D is provided at a position on an inner side of the spiral end position 16F of the involute spiral wrap 16B by an involute angle of π radians in the spiral direction or at a position on an outer side of the inner-side position when the orbiting scroll 16 including the stepped part 16E on the tooth bottom surface 16D is rotated to the position illustrated in FIG. 2(A), in other words, a state at intake closure.

Specifically, the stepped part 16E of the tooth bottom surface 16D is provided in a positional range on the inner side of the spiral end position 16F of the involute spiral wrap 16B of the orbiting scroll 16 by an involute angle of π/2 radians to π radians in the spiral direction. With this configuration, the stepped parts 16E and 15E are meshed with each other at intake closure at the position illustrated in FIG. 2(A), but the mesh between the stepped parts 16E and 15E is canceled immediately when rotation proceeds from the position illustrated in FIG. 2(A) to the position illustrated in FIG. 2(B) so that the pair of compression pockets 17 are communicated with each other. In this state, the internal pressures inside the pair of compression pockets 17 are at intake pressures having no pressure difference therebetween, and thus no mixing loss occurs due to gas mixture when the pair of compression pockets 17 are communicated with each other.

While 180° rotation is performed from the position illustrated in FIG. 2(A) to the position illustrated in FIG. 2(C) through the position illustrated in FIG. 2(B), the stepped parts 16E and 15E are not meshed with each other. During this rotation, a compression process proceeds while the pair of compression pockets 17 are communicated with each other. Then, at the position illustrated in FIG. 2(C), the stepped parts 16E and 15E become meshed with each other again. Further rotation by 90° completes 360° rotation, returning to the position illustrated in FIG. 2(A). Accordingly, the pair of compression pockets 17 at intake closure at the position illustrated in FIG. 2(A) move to compression pocket positions one step inside. Further rotation joins the pair of compression pockets 17 to discharge compressed gas into the discharge chamber 22 through the discharge port 18.

FIG. 4 is a graph illustrating change in the cylinder internal pressure (internal pressures in the compression pockets) through this process. Comparison with the graph of Comparative Example illustrated in FIG. 5 indicates that a mixing loss occurs near an scroll position angle of 650° in the graph of Comparative Example, but no mixing loss occurs in the graph of the present embodiment (in which the stepped part 16E is provided at a position on the inner side of the spiral end position of the involute spiral wrap 16B by an involute angle of π radians in the spiral direction).

Consequently, the present embodiment achieves effects described below.

When the electromagnetic clutch 12 is turned on in the scroll compressor 1 described above, power is input from a drive source to the drive shaft 6 through the pulley 11 and the electromagnetic clutch 12 to rotate the drive shaft 6. Accordingly, the orbiting scroll 16 coupled with the crank pin 13 of the drive shaft 6 through the driven crank mechanism 14 including the drive bush is driven to orbit about the fixed scroll 15.

When the scroll compressor 1 is driven in this manner, low-pressure refrigerant gas is sucked into the intake chamber 23 from the refrigeration cycle through the intake port 24, and then taken into the pair of compression pockets 17 through the orbital drive of the orbiting scroll 16. This refrigerant gas is compressed as the orbiting scroll 16 is rotated to move the compression pockets 17 from the outer side to the central site while the volumes thereof decrease. Then, the refrigerant gas is discharged into the discharge chamber 22 through the discharge port 18 provided at the central site of the fixed scroll 15, and then is sent to the refrigeration cycle.

During this process, the pair of compression pockets 17 at intake closure at the scroll position angle positions illustrated in FIG. 2(A) rotate by 360° sequentially through the position illustrated in FIG. 2(B), the position illustrated in FIG. 2(C), and the position illustrated in FIG. 2(D), returning to the position illustrated in FIG. 2(A) again. In the one-side stepped scroll compressor 1 according to the present embodiment in the state at intake closure illustrated in FIG. 2(A), the stepped part 16E only on the tooth bottom surface 16D of the involute spiral wrap 16B of the orbiting scroll 16 is provided at a position on the inner side of the spiral end position 16F of the involute spiral wrap 16B of the orbiting scroll 16 by an involute angle of π/2 radians to π radians in the spiral direction.

With this configuration, at the position illustrated in FIG. 2(A) at intake closure, the stepped parts 16E and 15E are meshed with each other, but when rotation is performed from the position illustrated in FIG. 2(A) to the position illustrated in FIG. 2(B), the mesh between the stepped parts 16E and 15E is immediately canceled so that the pair of compression pockets 17 are communicated with each other. In this state, internal pressures inside the pair of compression pockets 17 are still at intake pressures having no pressure difference therebetween. Accordingly, no mixing loss occurs when the pair of compression pockets 17 are communicated with each other to mix gasses thereof.

Thus, a mixing loss can be prevented from occurring due to the stepped part 16E provided in only one of the pair of compression pockets 17 in the scroll compressor 1 having the one-side stepped structure, thereby achieving improved efficiency accordingly. The efficiency can be further improved by reducing the number of places of stepped-part mesh gaps in the scroll compressor 1 having the one-side stepped structure from two to one to halve leakage of a working medium. In addition, cost reduction can be achieved by halving work for fabricating the stepped parts.

In addition, since the stepped part 16E on the tooth bottom surface 16D is provided in a positional range on the inner side of the spiral end position 16F of the involute spiral wrap 16B by an involute angle of π/2 radians to π radians in the spiral direction, the present embodiment can achieve an effect provided by an increased compression volume ratio due to the stepped part 16E, and simultaneously prevent a mixing loss occurring when the mesh between the stepped parts 16E and 15E is canceled so that the internal pressures in the pair of compression pockets 17 are mixed. Thus, the scroll compressor (scroll fluid machine) 1 can achieve increased efficiency through the stepped structure, reduction in size and weight, and further increased efficiency by preventing a mixing loss.

Other Embodiments

(1) Although the first embodiment describes above the open scroll compressor 1 having the one-side stepped structure in which the stepped part 16E is provided only on the tooth bottom surface 16D of the involute spiral wrap 16B of the orbiting scroll 16, the open scroll compressor 1 may have a one-side stepped structure in which a stepped part is provided only on the tooth bottom surface 15D of the involute spiral wrap 15B of the fixed scroll 15. This configuration can achieve effects same as those of the first embodiment.

(2) The first embodiment describes above the exemplary application to the scroll compressor 1 having a one-side stepped structure. In a scroll compressor having a both-side stepped structure in which stepped parts are provided to each of the fixed scroll 15 and the orbiting scroll 16 and have heights different between the fixed scroll 15 and the orbiting scroll 16, too, a pressure difference occurs between the pair of compression pockets 17 due to the different heights of the stepped parts. Thus, when the mesh between the stepped parts is canceled so that the compression pockets 17 are communicated with each other, a mixing loss occurs as described above.

For this reason, when the stepped parts provided to both scrolls have different heights in the scroll compressor having the both-side stepped structure, the stepped part on each tooth bottom surface is provided at a position on an inner side of the spiral end position of the corresponding involute spiral wrap at intake closure by an involute angle of π radians in the spiral direction or at a position on an outer side of the inner-side position. This configuration can achieve, for example, the effect of improving the efficiency by preventing a mixing loss, like the scroll compressor 1 having the one-side stepped structure described in the first embodiment.

The present invention is not limited to the above-described embodiments but may be modified as appropriate without departing from the scope of the invention. For example, although the embodiments describe the exemplary application to the open scroll compressor 1 above, application to a scroll expander, a scroll pump, and the like is possible. The present invention is not limited to the open scroll compressor 1 but is applicable to a scroll compressor including a compression mechanism and a motor.

REFERENCE SIGNS LIST

1 scroll compressor (scroll fluid machine)

15 fixed scroll

16 orbiting scroll

15A, 16A end plate

15B, 16B involute involute spiral wrap

15C, 16C tooth top surface

15D, 16D tooth bottom surface

15E stepped part on tooth top surface

16E stepped part on tooth bottom surface

16F involute spiral end position 

1. A scroll fluid machine comprising a pair of a fixed scroll and an orbiting scroll that include respective involute spiral wraps erected on end plates and meshed with each other in a facing manner, the scroll fluid machine having a one-side stepped scroll structure in which a stepped part is provided only at a predetermined position on a tooth bottom surface of the involute spiral wrap of one of the fixed scroll and the orbiting scroll in a spiral direction, and a stepped part corresponding to the stepped part of the tooth bottom surface is provided only at a predetermined position on a tooth top surface of the involute spiral wrap of the other scroll in a spiral direction, wherein the stepped part on the tooth bottom surface is provided at a position on an inner side of a spiral end position of the corresponding involute spiral wrap at intake closure by an involute angle of π radians in the spiral direction or at a position on an outer side of the inner-side position.
 2. A scroll fluid machine comprising a pair of a fixed scroll and an orbiting scroll that include respective involute spiral wraps erected on end plates and meshed with each other in a facing manner, the scroll fluid machine having a both-side stepped scroll structure in which stepped parts are provided at predetermined positions on a tooth top surface and a tooth bottom surface of the involute spiral wrap of each of the fixed scroll and the orbiting scroll in a spiral direction, wherein the stepped parts have heights different between the fixed scroll and the orbiting scroll, and the stepped part on each tooth bottom surface is provided at a position on an inner side of a spiral end position of the corresponding involute spiral wrap at intake closure by an involute angle of π radians in a spiral direction or at a position on an outer side of the inner-side position.
 3. The scroll fluid machine according to claim 1, wherein the stepped part on the tooth bottom surface is provided in a positional range on the inner side of the spiral end position of the corresponding involute spiral wrap by an involute angle of π/2 radians to π radians in the spiral direction.
 4. The scroll fluid machine according to claim 2, wherein the stepped part on the tooth bottom surface is provided in a positional range on the inner side of the spiral end position of the corresponding involute spiral wrap by an involute angle of π/2 radians to π radians in the spiral direction. 